Re: notifications

[Bas Wijnen]

Marcus Brinkmann wrote:
> > 8 - Task sends a message about it to A.
>
> Specifically, it replies to the IPC started in 1.

That's how A looks at it, however if I understood the L4 specs then 
there's no technical difference.  The only difference between doing send 
and receive in one or two calls is that doing it in one is an atomic 
operation (while two calls could result in a "too fast" reply which 
cannot be handled yet.)

> > 9 - C dies.
> > 10- Task waits (and does _not_ notify A yet.)
>
> Be precise.  We want to define what "notify" means, so you can't use
> that term.

Oh, I didn't think I was defining it.  Notify means for me to make the 
information available in any way.

> Better: It can not send a message to A because there is no
> request to reply to.

I don't like to use the word "reply", because it suggests (to me at 
least) that the IPC is started as a direct result of the request.  For A 
it looks like a reply of course, but for task it's just an IPC.

> Note that you can also cancel
> the IPC from 1 and let that thread handle the request for more
> notifications in its next request (this makes things more
> synchronous, and may be desirable or not).

If the IPC is cancelled while waiting (so task is not in an IPC), would 
task get notified?  Or would its reply IPC return immediatly with error 
set?  That doesn't make sense to me.  I'm probably misunderstanding you, 
could you please clarify?

Thanks,
Bas

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